Go BottomWoods rotary mower and gearbox leaks
 | Roger L.
Join Date: Jun 1999 Posts: 0 
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2000-07-04 17691
I've just had good luck fixing an oil leak on my Woods M5 rotary mower and though I'd share the method. The M5 is a locally common rather heavily built bushhog type mower and it had a problem: The gearbox would leak dry in an hour of use. The problem was obviously the bottom seal between the gearbox and the blade. Instead of replacing the seal I put in a mixture of carquest Engine stop leak, along with the normal oil and grease. This seemed to show down the leak a little and was worth the effort. But what really fixed the problem was noticing that this gear box is not vented! I drilled a hole to vent the inspection cover and the oil no longer leaks out past the seal...although it does sometimes foam out through the vent - confirming that a vent is necessary.
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 | Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada 
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2000-07-04 17695
We had a similar problem with several pieces of pto driven equipment also. Instead of drilling a hole in the gearbox though I discovered that the 'fill' plug was a 3/4" NPT thread, and I replaced them all with 'breather caps' for a hydraulic reservior, the difference being these caps have very small filters built in to prevent contamination from debris, water, etc. However I must also add at this point that if this is done the lubricant in the gearbox MUST be changed far more often because with the heat/cool cycle condensation accumulates very quickly causing premature breakdown of the lubricant. All in all this is better than running a gearbox empty..... Best of luck. ....
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| Roger L.
Join Date: Jun 1999 Posts: 0
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2000-07-05 17725
I think I know what type of breather that you are talking about. Mine inspection plug is also NPT, so a filter plug would be the better solution if it would fit. There isn't much room, because Woods put the inspection hole centered right under the upper support to the top of the three point. You actually have to take a piece of the three point connecting arm off in order to check the oil or add any!
One day I was looking at that no-brain plug location in awe and wonder and it dawned on me that anyone who would put the plug there might also forget to design in a vent hole in the gearbox....turned out to be true.
But nothing is perfect. The Woods M5 is one of the best bushhog type mowers ever built when one looks at the strength of the metal, the size and support of the gearbox (very important), and the geometry of the 3 pt and trailing wheel...in fact everything about that M5 is excellent - except that silly missing vent. ....
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| Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2000-07-05 17729
Roger, I suspect it is more to do with cost considerations (using an existing gear-box from a third-party supplier, or previous casting) than lack of engineering prowess. In theory it doesn't matter much where the vent goes, provided it is sufficiently above the 'full mark'. Try using some short pieces of black-pipe and a couple elbows to bring the drain opening (presuming it is more accessable) up high enough that the gear-box can be vented by allowing the fluid to 'burp' or draw air as it heats and cools without spewing fluid everywhere. I did this on a 'grander scale' and connected both openings to a 1 gallon hydraulic reservoir in order to create a 'cooling system' for the gear-box on our bigg tiller. ....
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| Roger L.
Join Date: Jun 1999 Posts: 0
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2000-07-05 17738
I hear you, Murf. But in this case it was strictly a manufacturing oversight. The top plate for the casting is original, and nothing more than an 8" square piece of 3/32 steel with 4 holes punched for bolting to the casting plus a center hole broched and tapped for NTP. A vent would have been simple to add. I will tap a hole and put in a U tube vent in the approriate place - far above the fluid level.
The only reason why I brought it up is that someone else might be having mysterious leakage past the seals their bushhog's gearbox, too. I put up with the leak for years before finally getting down and taking a critical look at the design... ....
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